That was an observation from Karl Krantz, co-founder of the Silicon Valley Virtual Reality conference. He'd been telling me about his experience with the HTC Vive—the virtual reality headset made by HTC and powered by video game maker Valve. His point was just how important interactivity will be as more and more people get introduced to virtual reality. If one of the main selling points of VR is immersion, then actively engaging in a virtual world versus passively experiencing it could be the difference-maker.

After getting to demo of the Vive at the Valve office in Seattle recently, I have to agree.

High-end virtual reality has three big players: Vive, Oculus Rift (backed by Facebook), and Sony's Playstation VR. Only Oculus and Vive are geared toward PC-based gaming, and they've been getting the bulk of the buzz. However, only Vive and Playstation VR will ship with hand controllers.

Hand controllers are an odd animal. They don't look cool—in truth, nothing about VR looks cool, but the thing to remember is that when you've got controllers in your hands and you're experiencing an engaging demo, you're not thinking about that. You're thinking about the virtual world that you're getting to manipulate.

I got to do a handful of demos with the Vive. The most fun was Tilt Brush, a sandbox-type experience that lets the user paint and draw in three dimensions. It's really less painting and more sculpting, because if you draw a picture as you would on paper, you can actually walk around it and see layers in space. It's striking to be able to stand in the middle of your own art project.

Apparently, I'm not the only one impressed. At the Augmented World Expo in Santa Clara last June, a panel on VR content featured Ben Miller, director of content for Venice Beach-based VR company WEVR. The inevitable question came up as to what the killer app for VR might be, he said he thought it might be something open-ended and sandbox-y.

Google seems to think something similar, since it acquired Tilt Brush in April.

Other demos included Job Simulator, in which a robot directs the viewer on how to make a recipe. That includes opening a refrigerator door, shaking a salt shaker, squeezing condiments into a pot, cracking eggs—that sort of thing.

Another was an interactive story in which humans are being tested for their ability to repair robots. At one point, the viewer uses the controller to pull apart the parts of a robot. It's easy to see what makes up the machine as the parts are suspended in space.

Yet another, speaking of WEVR, was The Blu. The viewer gets to stand underwater on the bow of a wrecked ship and watch a massive baby whale swim by. Interactivity here comes in the ability to swat away tiny fish that get too close. While that may sound like a small thing, it's an example of how real it feels in VR when something invades your personal space.

1. These controllers are good enough that despite the fact they're in your hands, mentally, they're out of your way. Once you learn where the dial is and the trigger, it's a very short jump to get them to do what you want. One particularly fun demo was basically archery practice. The viewer can reach back into her quiver to get an arrow, and then she pulls the arrow back, the haptics in the other controller communicate the tension in the bow.

2. Many of these demos had elements that could be carried over to more business-related applications—things like exploded diagrams for parts, training, 3D modeling, or education. But what makes all those applications useful is the interactive element.

3. As Krantz said, it becomes less satisfying to experience a virtual world as if you're in a glass case, unable to reach out and touch anything—if you go from something like the Vive back to Oculus Rift (which is working on its own "halfmoon" controllers, but they won't be available at launch). As consumers gain exposure to higher-end virtual reality, they'll expect more, and interactivity will be an important part of it.

Eventually—hopefully sometime within 2016—the conversation will turn from who has hand controllers, to who has the best ones.